1. Field of the Invention
The present invention relates to a method for separating a basic amino acid from a fermentation broth.
2. Background Art
Lysine and other basic amino acids are used extensively as animal feed supplements. Typically, lysine is produced by the fermentation of dextrose. In addition to lysine, the fermentation broth contains a variety of impurities, such as color bodies, residual sugars, salts, and other by-products. The primary step in the purification of lysine from fermentation broth is ion exchange chromatography (Tanaka, et al., U.S. Pat. No. 4,714,767 (1985)). The chromatographic separation can be operated in batch or continuous mode using fixed bed or simulated moving bed technology (Van Walsern, H. J., and Thompson, M. C., J. Biotechnol., 59:127-132. (1997)). Typically strong acid cation exchange resins with a high degree of cross-linkage are used.
Simulated moving bed (SMB) technology is a convenient and efficient method of chromatographic separation of fermentation broth (Broughton, D. B., U.S. Pat. No. 2,985,589(1961)). When traditional strong acid cation exchange resins, with a high degree of cross-linkage, are used in SMB operation, the purity of lysine obtained is only 80-85%, with a yield of about 85-90%. This low level of separation obtained with traditional strong acid cation exchange resins that have a high degree of cross-linkage may not be satisfactory for industrial-scale production. There is therefore a need to improve the purity and yield of lysine during the purification of fermentation broth.
The present invention relates to a method for separating a basic amino acid from fermentation broth using simulated moving bed technology, comprising contacting the fermentation broth with strong acid cation exchange resins that have a low degree of cross-linkage, and eluting the amino acids from the exchange resins.